Heretofore, dyeing of this kinds of protein fiber products is generally carried out in an acidic dyeing bath at a boiling temperature. Thus, various troubles such as yellowing, shrinkage, lowering in strength of protein fiber, and difficulty in color matching due to yellowing, and the like are generated. Accordingly, the conventional protein fiber dyeing technique is not necessarily optimum in view of obtaining protein fiber products with high quality, high added value and low energy cost.
On the other hand, in order to solve these problems, there have been investigated a low-temperature dyeing method comprising an easily dyeing treatment of protein fiber such as an ammonia pre-treatment, an enzyme pre-treatment, a 1-propanol treatment, an alkaline agent treatment, etc.
However, these dyeing method at a low-temperature has not yet been practically used by the reasons as mentioned below. That is, whereas the ammonia pre-treatment has been admitted to as effective for obtaining an easily dyeing effect, various problems related to its volatility and irritating odor have occurred. Also, the oxygen pre-treatment is effective for easy dyeing, but according to the present situation, it requires a high cost, and yet there involves problems that dyeing fastness of the resulting dyed material is likely low and a generation ratio of dyeing unevenness is high. Further, the 1-propanol treatment involves the problem that a uniform effect can be hardly obtained unless a large amount of a treating agent is used. Moreover, the alkaline agent treatment is effective for easy dyeing, but it involves the problem that a uniform effect cannot be obtained since the alkaline agent is too strong in a property as a donor.
An object of the present invention is to provide a low-temperature dyeing additive for protein fiber products, which serves to relax the high-order structures of the protein fibers before dyeing or during dyeing thereby swell the fibers without impairing physical properties thereof.
Another object of the present invention is to provide a method of dyeing protein fiber products with high quality and high dyeing density without impairing physical properties thereof after treating or while treating the protein fibers with the low-temperature dyeing additive.